Selective access of multi-rate data from a server and/or peer

ABSTRACT

Aspects of the disclosed subject matter are directed to facilitating peer-to-peer data exchange in a common domain. In accordance with one embodiment, a method is provided for obtaining content from one or more peers that are connected to the domain. The method includes registering a peer with a super-peer when a connection to the domain is established. Then, the connecting peer obtains data that describes various network conditions and identifies chunks of content available from other peers. In downloading content from other peers, heuristics are applied to select between available chunks that are potentially encoded at different bitrates. The heuristics account for the network conditions between peers and balance the potential need to quickly access content with the desire to obtain high quality content.

CROSS-REFERENCE(S) TO RELATED APPLICATION(S)

This application is a continuation of commonly owned U.S. patentapplication Ser. No. 15/425,912, filed Feb. 6, 2017, entitled “SELECTIVEACCESS OF MULTI-RATE DATA FROM A SERVER AND/OR PEER,” which is acontinuation of commonly owned U.S. patent application Ser. No.12/791,789, filed Jun. 1, 2010, entitled “SELECTIVE ACCESS OF MULTI-RATEDATA FROM A SERVER AND/OR PEER,” now U.S. Pat. No. 9,565,239, whichclaims the benefit of U.S. Provisional Patent Application Ser. No.61/182,656, filed May 29, 2009, entitled “SELECTIVE ACCESS OF MULTI-RATEDATA FROM A SERVER AND/OR PEER”, which is hereby incorporated in itsentirety by reference.

BACKGROUND

Streaming distribution of live and on-demand audio and/or video over theInternet is challenging due to the dynamic nature of various elementsutilized in the delivering and rendering of content. Traditionally,users would have to select a specific bitrate to match their expecteddownload speeds, or would allow an automated detection system to selectthe appropriate bitrate. However, bandwidth conditions changedynamically, and bandwidth availability may drop dramatically over thecourse of a sustained connection. To compensate for such changes, a usermay consider selecting the lowest offered bitrate for a given piece ofcontent, in consideration of the likelihood that network conditions willdeteriorate from a peak at the beginning of the connection.

The market penetration of High Definition (HD) media delivery hassuffered from this phenomenon, as it is not typical that an end userwill have sufficient bandwidth to sustain a bitrate for transmission ofan entire HD-quality media stream that is longer than a few minutes.Additionally, scaling delivery of HD content to serve ever-increasingnumbers of users is difficult as the high quality of the content alsoconsumes server bandwidth. This higher server bandwidth increases servercosts, especially when attempting to preserve guaranteed quality ofservice metrics.

While multiple solutions exist that attempt to solve problems inproviding large quantities of HD-quality media over the Internet, theseexisting solutions all have drawbacks. One such solution purportedlyallows storing a single media presentation in multiple differentbitrates, and indexing each version to allow switching between versionsas network conditions change and bandwidth fluctuates. However, thesetypes of solutions have drawbacks when attempting to provide smoothtransitions between bitrates, due to the location of keyframes. Also,this solution continues to use a centralized download source, which doesnot scale well and may result in “bottlenecking” problems as describedabove.

Peer-to-peer solutions for providing massive media download capabilitieshave also emerged. However, these existing solutions are not well suitedfor providing streaming of live content. Generally, such solutions breakthe content into fragments which are distributed among multiple peersystems. When a client downloads a file from the peer-to-peer networkusing these existing technologies, it may not take into account theorder of the fragments requested, which makes it difficult or impossibleto deliver media in a streaming format. Another problem with existingpeer-to-peer solutions is that they generally require installation ofstand-alone client software on each peer. End users are increasinglywary of installing native executables from untrusted sources. As such,requiring such client software to be installed will decrease thepopularity of any peer-to-peer system.

Even more problems arise when attempting to increase acceptance bybuilding a peer-to-peer distribution system to run within a generic hostapplication such as a web browser. Web browsers allow rich applicationcontent to be executed without installing additional software on thelocal system. However, web browsers typically segregate access to localresources based on domains. In other words, when a web application isconnected to the “foo.com” domain, the web application is only able toaccess local storage related to the “foo.com” domain. Once the webbrowser is directed to a different domain, the local content from the“foo.com” domain is inaccessible. Hence, the number of peers in apeer-to-peer distribution system is limited to peers who are currentlyaccessing the same domain, and these peers will be unavailable whenusers navigate away from that domain. Further, web browsers can allowmore than a single copy of a web site to be viewed at a single time.This means that a peer-to-peer application running on such a web sitewould either run into collisions when both copies attempt to open thesame client port, or that each copy would select a different port, andcould not be located by peers attempting to connect to a well-known peerclient port. Existing peer-to-peer distribution systems are notcurrently able to operate with such high unpredictability in peeravailability and contact information.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

Aspects of the disclosed subject matter are directed to facilitatingpeer-to-peer data exchange in a common domain. In accordance with oneembodiment, a method is provided for obtaining content from one or morepeers that are connected to the domain. The method includes registeringa peer with a super-peer when a connection to the domain is established.Then, the connecting peer obtains data that describes various networkconditions and identifies chunks of content available from other peers.In downloading content from other peers, heuristics are applied toselect between available chunks that are potentially encoded atdifferent bitrates. The heuristics account for the network conditionsbetween peers and balance the potential need to quickly access contentwith the desire to obtain high quality content.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thedisclosed subject matter will become more readily appreciated as thesame become better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a block diagram depicting an exemplary environment wheredescribed embodiments of the disclosed subject matter can beimplemented;

FIG. 2 is a general block diagram of an exemplary device in accordancewith some embodiments of the disclosed subject matter;

FIG. 3 is a general block diagram of an exemplary device in accordancewith some embodiments of the disclosed subject matter;

FIG. 4 is a block diagram depicting an exemplary environment wheredescribed embodiments of the disclosed subject matter can beimplemented;

FIG. 5 is a flow diagram of a routine for registering with a super-peerin accordance with some embodiments of the disclosed subject matter;

FIG. 6 is a flow diagram of a routine for obtaining content from one ormore peers in accordance with some embodiments of the disclosed subjectmatter; and

FIG. 7 is a general block diagram depicting a state machine suitable forillustrating additional aspects of the disclosed subject matter.

DETAILED DESCRIPTION

Aspects of the present disclosure are directed to a domain-basedpeer-to-peer network that allows users to access content frompotentially multiple peers. The examples provided below may describefunctionality of the present disclosure with reference to obtainingmedia data such as streaming video and audio However, those skilled inthe art and others will recognize that the present disclosure may beapplied to exchange other types of data without departing from the scopeof the claimed subject matter. Moreover, the illustrative examples anddescriptions provided below are not intended to be exhaustive or tolimit the claimed subject matter to the precise forms disclosed.Similarly, any steps described below may be interchangeable with othersteps or combinations of steps in order to achieve the same orsubstantially similar result.

FIG. 1 illustrates one embodiment of a peer-to-peer content distributionsystem 100 according to various aspects of the present disclosure. Thesystem 100 will be described from the perspective of a peer 102 for easeof discussion, but it will be recognized by one of skill in the art thateach of the peers 104, 106, 108 are essentially interchangeable withregard to this discussion.

As illustrated, client peer 102 is a computing device coupled to a widearea network 90 and a local area network 92. In one embodiment, clientpeer 102 is a desktop computer, but in other embodiments client peer 102can be any device capable of connecting to a network and executing ageneric web browser. Client peer 102 uses its generic web browser toconnect to a source server 110, which provides a web application thatenables peer-to-peer communication. The other peers 104, 106, 108 arealso executing the web application that enables peer-to-peercommunication, and are visiting the same domain as the client peer 102.

Upon startup, client peer 102 finds and connects to one of a pluralityof super-peers such as super-peers 112-114. In one embodiment,super-peers 112-114 are specialized servers adapted to act assuper-peers. In another embodiment, super-peers 112-114 aresubstantially similar to the other peers taking part in the system 100,but have been elected or otherwise designated to act as a super-peer.The super-peers 112-114 each store information identifying the otherpeers participating in the system 100. As described in further detailbelow, the client peer 102 requests information from one of theplurality of super-peers 112-114, in order to identify and connect toremote server peers 104, 106, and local server peer 108. The informationstored by the super-peer is described in further detail below.

Once connected to one or more of the remote server peers 104, 106 andthe local server peer 108, client peer 102 determines a plan fordownloading content such as a media file. This plan can take intoconsideration which peers have the various portions of the media file,and can also take into consideration variable amounts of bandwidthavailable between the client peer 102 and other portions of the system100. For example, in a traditional media download model, the client peer102 downloads the entire media file from a centralized location such asoriginal source server 110. However, in the peer-to-peer model, it canbe more efficient to download the media file in chunks from a multitudeof different servers.

In the illustrated example, client peer 102 has a network connection 116through the wide area network 90 to the source server 110 capable oftransmitting data at 1 Mbps. Client peer 102 has a similar networkconnection 118 to a first super-peer 112. Client peer 102 has a slowernetwork connection 120 to a second super-peer 114 that is only capableof transmitting data at 0.5 Mbps. Meanwhile, client peer 102 has afaster network connection 124 to a remote server peer 106 capable of 5Mbps data transfer, and an even faster network connection 122 to aremote server peer 104 capable of 10 Mbps data transfer. As each ofthese network connections transmits across the wide area network 90,each is slower than the network connection 126 to a local server peer108, which is capable of 1 Gbps data transfer. These differences innetwork speeds can be due to the inherent nature of the networkingtechnology used (such as communicating over a wide area network 90 asopposed to a local area network 92), and can also be due to transientconditions and/or geographic location on the network (such as highlevels of concurrent traffic or other network bottlenecks between thehosts).

In the illustrated example, client peer 102 selects servers from whichto request data based on the available network bandwidth. For example,client peer 102 can choose to request peer information from super-peer112 instead of super-peer 114 due to the higher speed connection. Asanother example, client peer 102 can attempt to obtain as much of themedia file from local peer server 108 as possible, and can refrain fromresorting to the lower speed connections to remote server peer 104 andremote server peer 106 until a portion of the media file is needed thatis not available from the local server peer 108. In this way, clientpeer 102 is able to maximize the quality of the downloaded media file byusing the highest bandwidth connection available, even when networkconditions or peer availability change during the download.

FIG. 2 illustrates one embodiment of a source server 200 according tovarious aspects of the present disclosure. Source server 200 is similarto source server 110 illustrated above and includes source chunk storage202 and a chunk server 208. The source chunk storage 202 stores acomplete copy of a source data 204 which, in this example, represents amedia file. This source data 204 is then divided into a plurality ofchunks 206 of varying levels of quality. As illustrated, the source data204 is broken into three large pieces A, B, C, which are encoded fortransmission at bit rate 1. In this example, bit rate 1 is the highestavailable bit rate, which results in a larger chunk being transferredbetween the source server 200 and a client peer. The source data 204 isalso broken into three somewhat smaller chunks A′, B′, C′ fortransmission at bit rate 2. In this regard, bit rate 2 is lower than bitrate 1, so the chunks A′, B′, C′ are smaller and may be transferred inapproximately the same amount of time as chunks A, B, C, but at thelower bit rate. Likewise, the source data 204 is broken into evensmaller chunks A″, B″, C″ for transmission at bit rate 3, the lowestsupported bit rate.

Chunk server 208 sends chunks 206 to client peers upon request. In oneembodiment, the client peer requests a given chunk at a given bit rate.In other embodiments, the client peer requests a given chunk, and thechunk server 208 determines an appropriate bit rate before sending thechunk. Chunk server 208 can also provide the web application thatinitially directs the peer-to-peer client to the client peer.

In one aspect, one or more of the elements of source server 200 can beincluded in a peer, such that source server 200 would have similarbehavior to any of the other peers in the system 100, with the exceptionof always being available and containing a complete copy of the sourcedata 204.

FIG. 3 illustrates one embodiment of a peer 300 according to variousaspects of the present disclosure. The illustrated peer 300 functions asboth a client peer 102 and as a server peer 104, 106, 108 at varioustimes. The peer 300 executes a host application 302. One example of anappropriate host application 302 is a general purpose web browser,though other host applications can be used without departing from thescope of the claimed subject matter.

In the example illustrated in FIG. 3, host application 302 hosts apeer-to-peer stack 304 and a heuristic engine 310 provided by thepresent disclosure. The peer-to-peer stack 304 manages communicationsbetween the peer 300 and other peers, as well as between the peer 300and one or more super-peers. This communication at least includesdownloading chunks, downloading information about other peers,registering the peer 300 with a super-peer, and sensing networkconditions. The heuristic engine 310 analyzes the downloadedinformation, and stores the analyzed heuristic data in the heuristicdata storage 312. In this regard, the heuristic data may include but isnot limited to the identity and location of fellow peers, networklatency and bandwidth between the peer 300 and other points in thepeer-to-peer network, identity of chunks available at each fellow peer,location and identity of super-peers, among others. After building aninitial “weather map” of the network, the heuristic engine 310 continuesto monitor the communications of the peer-to-peer stack 304, and updatesthe stored heuristic data to reflect changing network conditions. Thedata stored in the heuristic data storage 312 includes historical datafor previous connections, which helps improve predictions generated bythe heuristic engine 310.

As discussed above, the host application 302 segregates local resourceaccess based on the domain that the host application 302 is accessing.Peer chunk storage 306 of the host application 302 is illustrated asstoring peer chunks 308 corresponding to the same domain as illustratedin FIG. 2. FIG. 3 illustrates an exemplary state of peer chunk storage306 after having accessed an entire source content. Early in the contentwhen the peer 300 is attempting to fill a buffer, the peer 300 typicallydownloads smaller chunks such as A″ and B″ to ensure that an adequateamount of data will be available to initiate playback of the content.Later, when the buffer is full and the heuristic engine 310 is moreaggressive about the amount of time available to download content,larger chunks such as B′ and C are downloaded. These heuristictechniques are described further below.

FIG. 4 illustrates one embodiment of a peer-to-peer topology 400according to various aspects of the present disclosure. When thepeer-to-peer stack 304 of client peer 402 first accesses a given domain,it opens a connection endpoint referencing a local port that is notcurrently in use. If no other peer-to-peer stacks are executing onclient peer 402, the new peer-to-peer stack can open a default port. Ifanother peer-to-peer stack is already executing on client peer 402, thenew peer-to-peer stack opens a different port. The port being opened canbe chosen according to a predetermined order, randomly, or by any otherappropriate method known to those of skill in the art.

Next, the peer-to-peer stack 304 of the client peer 402 opens aconnection to a super-peer 404 which may be found in a number ofdifferent ways. The location of the super-peer 404 can be well-known,and the peer-to-peer stack 304 would merely need to connect to thewell-known location. In another embodiment, the location of thesuper-peer 404 changes, and the peer-to-peer stack 304 searches for thelocation of the super-peer 404 by broadcasting packets to, for example,a source server, other previously connected peers, and the like.

Once connected to the super-peer 404, the client peer 402 informs thesuper-peer 404 of the address, port, and domain being used by the clientpeer 402. In one embodiment, the super-peer 404 stores this informationin a peer identification store 406 along with similar information forother peers. Once registered, the client peer 402 then receivesinformation from the super-peer 404 concerning the address, port, anddomain being used by other peers in the peer-to-peer topology 400.

The client peer 402 uses the information obtained from the super-peer404 to contact the other peers. For example, client peer 402 can attemptto contact each of the peers identified by the super-peer 404 todetermine if the information stored by the super-peer 404 is stillvalid. That is, if a peer disappears from the peer-to-peer topology 400through the loss of a network connection, a change in domains, and thelike, the peer may or may not notify the super-peer 404 it is leavingthe peer-to-peer topology 400. An attempt by the client peer 402 tocontact each of the identified peers ensures that the state informationis current.

Once the client peer 402 determines that a given peer is online andavailable, the client peer 402 requests chunk information from the otherpeers, and analyzes the network conditions over the path of theconnection. For example, client peer 402 contacts server peer A 416,which is active in domain “foo.com” on port 9865, and requests its chunkinformation. Server peer A 416 responds and indicates that its peerchunk store 408 contains low bitrate peer chunk A″ and low bitrate peerchunk B″. From this response, client peer 402 determines that theavailable bandwidth of the network connection 426 between client peer402 and server peer A 416 is 1 Mbps. A similar information exchangeoccurs between client peer 402 and server peer B 418. As illustrated inFIG. 4, peer B 418 stores high bitrate peer chunk A in the peer chunkstore 410, which is capable of being transmitted over the networkconnection 428 at 1 Mbps.

Though server peer C 420 has relevant peer chunks B′ and C in its peerchunk store 412, the peer identification information indicated thatserver peer C 420 is currently active in domain “bar.com.” In oneembodiment, client peer 402 will therefore not attempt to contact serverpeer C 420. In another embodiment, client peer 402 nevertheless recordsthe existence of server peer C 420 and the bandwidth of its networkconnection 430 in its heuristic data storage 312, in case thisinformation could be of use in the future. In this example, client peer402 attempts to contact server peer D 422, but finds that the networkconnection 432 between client peer 402 and server peer D 422 isinaccessible.

Client peer 402 stores the information received from the server peers inits heuristic data storage 312. In displaying a streaming media file,the order in which chunks are obtained matters as the content isdisplayed sequentially. The portions of the content can be obtained outof order, but the display of the media file cannot begin until someversion of the first portion is retrieved. The heuristic engine 310 usesthe received information to develop a plan for downloading the highestpossible quality portions of the media file, while maintainingconsistent playback of the media.

Many different heuristic strategies can be deployed for downloading thepeer chunks. In one embodiment, the heuristic engine 310 calculates howmany low-bandwidth peer chunks would have to be downloaded to fill abuffer, and plans to download that many peer chunks, in chronologicalorder, until the buffer is full. Once the buffer is full, the heuristicengine 310 may seek higher bandwidth peer chunks, either to replacechunks that have already been downloaded, or as new chunks for later inthe presentation. Early in the presentation, the heuristic engine 310can prefer connecting to peers with low-bandwidth peer chunks tomaximize the speed of filling the buffer, and can switch later in thepresentation to prefer connecting to peers with known reliable, highbandwidth connections with the client peer 402.

In the illustrated example, client peer 402 would begin searching forserver peers that have some version of portion A. Client peer 402 findsthat both server peer A 416 and server peer B 418 have versions ofportion A. Given that playback should be initiated quickly, client peer402 will likely choose to download chunk A″ from server peer A 416,despite the higher quality of chunk A on server peer B 418, to maximizethe speed with which the presentation to the user can begin. However,higher quality chunks may be selected in instances when performancewould not be substantially affected.

FIG. 5 illustrates one embodiment of a method 500 of registering aclient peer 102 with a super-peer 112. From a start block, the method500 proceeds to block 502, where a host application 302 of the clientpeer 102 connects to a domain and downloads domain presentation layerdata. In one example, connecting to a domain could include connecting toa news web site and downloading an HTML page, JavaScript, or othersimilar data that defines the presentation of the content. Next, atblock 504, the host application 302 starts a peer-to-peer stack 304 inresponse to an instruction by the domain presentation layer data. Themethod 500 then proceeds to block 506, where the peer-to-peer stack 304finds an available super-peer 112. As discussed above, the peer-to-peerstack 304 can use one of a number of techniques for finding thesuper-peer 112, such as transmitting broadcast packets or attempting toconnect to a known good address.

Next, at block 508, the peer-to-peer stack 304 transmits client peerregistration data to the super-peer 112. This registration data includesa port number that the peer-to-peer stack 304 is listening to, anaddress of the client peer 102, and the domain on which client peer 102is active. The method 500 then proceeds to block 510, where thepeer-to-peer stack 304 receives information that identifies other activesuper-peers from the available super-peer 112. The peer-to-peer stack304 may store this information for future reference, in case theavailable super-peer 112 is taken offline or is otherwise unreachable.Next, at block 512, the peer-to-peer stack 304 receives informationidentifying other active peers connected to the domain from theavailable super-peer 112. As discussed above, this information includesnetwork status information, peer chunk availability, and the like. Themethod 500 then proceeds to an end block and terminates.

FIG. 6 illustrates one embodiment of a method 600 of downloading datafrom peers. From a start block, the method 600 proceeds to block 602,where a peer-to-peer stack 304 of a client peer 102 receives chunkinformation from one or more server peers. Next, at block 604, thepeer-to-peer stack 304 stores the chunk information and network statusinformation that relates to each of the one or more server peers. Themethod 600 then proceeds to block 606, where the peer-to-peer stack 304optionally transmits the chunk information and network statusinformation to a super-peer 112. In embodiments that employ thisoptional step, the client peer 102 can download the chunk informationand network status information directly from the super-peer 112, whichincreases the speed of the initial collection of heuristic data andprovides greater historical information on which to base the heuristicdecisions.

Next, at block 608, a heuristic engine 310 of the client peer 102analyzes the chunk information and the network status information. Themethod 600 then proceeds to block 610, where the heuristic engine 310generates a download plan for accessing particular content using theobtained chunk information and the network status information. Next, atblock 612, the peer-to-peer stack 304 begins downloading data chunksfrom one or more server peers according to the download plan. The method600 then proceeds to block 614, where the heuristic engine 310 monitorsfor changes in the chunk information and the network status information,and updates the download plan accordingly. The heuristic engine 310 canperiodically ping the super-peer 112 to access current information aboutvarious network conditions and other peers. The heuristic engine 310 canalso ping the server peers directly to determine their status, or caneavesdrop on the communication between the peer-to-peer stack 304 andthe server peers during the course of downloading the content. Next, themethod 600 continues to an end block and terminates.

In one aspect, the heuristic engine 310 adapts the download planaccording to multiple goals. These goals include starting thepresentation without delay and providing as high a quality presentationas possible. As such, the heuristic engine 310 balances the goal ofkeeping a play buffer substantially full with content from a chunk evenif the chunk is of low quality, versus finding high-quality chunks thatwill be transferable in the time needed to keep the buffer full. FIG. 7illustrates a state diagram 700 that illustrates how one embodiment ofthe heuristic engine 310 balances these goals. When a download isinitiated, the heuristic engine 310 enters the fill state 702. In thisstate, the heuristic engine 310 searches the peer-to-peer topology forchunks that will fill the beginning of the play buffer as quickly aspossible. Moreover, in the fill state 702, the heuristic engine 310prioritizes high bandwidth connections over low bandwidth connections,and peers that have early chunks over late chunks.

Once the play buffer is full, the heuristic engine 310 follows atransition 708 into the maintain state 704. In the maintain state 704,the heuristic engine 310 attempts to maximize the quality of thepresentation given the network conditions. In this case, the heuristicengine 310 prioritizes high-quality chunks over low-quality chunks, andis less concerned with bandwidth or the position of the chunk in thepresentation. Hence, the heuristic engine 310 can choose to begindownloading a high quality chunk that is later in the presentation overa medium quality chunk that is earlier in the presentation, given thatadequate time is likely available to obtain the earlier chunk before thebuffer is empty.

If the buffer does empty to the point where smooth playback is in dangerof being interrupted, the heuristic engine 310 follows a transition 710into the recover state 706. The recover state 706 is similar to the fillstate 702, in that earlier, lower quality chunks will be given higherpriority. Once the heuristic engine 310 has managed to fill the bufferback up to a predetermined amount, the heuristic engine 310 follows atransition 712 back into the maintain state 704.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A method implemented in computer-executableinstructions for: registering, based at least in part upon a first peerconnecting to a domain, the first peer with a super-peer, wherein thesuper-peer stores information identifying one or more other peers in thedomain; obtaining data that describes network conditions and identifieschunks of content available from the one or more other peers; whereinthe chunks of content available from the one or more other peers havepreviously been encoded for transmission at different bitrates;selecting a first chunk of content to download from a second peer of theone or more other peers in the domain, wherein the selection is based,at least in part, on a bitrate for which the first chunk of content hasbeen encoded for transmission and a size of the first chunk of content,and an amount of bandwidth that is available for a connection betweenthe first peer and the second peer; downloading the first chunk ofcontent from the second peer; detecting a change in network conditions;selecting a second chunk of content to download from a third peer of theone or more other peers in the domain, wherein the selection of thesecond chunk of content is based, at least in part, upon a bit rate forwhich the second chunk of content has been encoded for transmission, asize of the second chunk of content, and an amount of bandwidth that isavailable for a connection between the first peer and the third peer;and downloading the second chunk of content from the third peer to thefirst peer.
 2. The method of claim 1, wherein the first peer makes peerselections to maximize bandwidth for downloading the first chunk ofcontent from the second peer.
 3. The method of claim 1, wherein theselecting the chunk of content comprises at least one of: the first peerrequests the first chunk of content be downloaded at a specified bitrate; the first peer requests the first chunk of content be downloaded,and the super-peer determines an appropriate bit rate for downloadingthe first chunk of content; or the super-peer provides a web applicationthat directs the first peer to the second peer that will download thefirst chunk of content to the first peer.
 4. The method of claim 1,further comprising managing communications between the one or more otherpeers and the super-peer using a peer to peer stack, wherein theobtaining data comprises storing heuristic data about the one or moreother peers on the domain using a heuristic engine.
 5. The method ofclaim 4, wherein the heuristic data include one or more items selectedfrom the group consisting of: an identity of the one or more other peerson the domain; a location of the one or more other peers on the domain;a network latency; an available transmission bandwidth between points inthe domain; an identification of chunks of content available at the oneor more other peers on the domain; a location of super-peers on thedomain; and an identity of super-peers on the domain.
 6. The method ofclaim 4, further comprising using the heuristic engine to monitor thecommunications of the peer to peer stack, and to update the heuristicdata that is stored, to reflect changing network conditions.
 7. Themethod of claim 4, wherein selecting the first chunk of content todownload to the first peer comprises using the heuristic engine todetermine how many successive chunks of content that are encoded fortransmission at relatively low bit rates should be downloaded to fill abuffer of the first peer, and downloading the successive chunks ofcontent until the buffer is full.
 8. The method of claim 7, furthercomprising using the heuristic engine to identify chunks of content thathave been encoded for transmission at relatively higher bit rates, andafter the buffer of the first peer is full of the successive chunks ofcontent encoded for transmission at the relatively low bit rates, eitherreplacing the successive chunks of content that have already beendownloaded, with corresponding chunks of content that were encoded fortransmission at the relatively higher bit rates, or downloading furthersuccessive chunks of content encoded for transmission at the relativelyhigher bit rates.
 9. The method of claim 4, wherein selecting the firstchunk of content to download comprises initially preferentiallydownloading chunks of content from one or more peers connected to thefirst peer over a relatively low bandwidth connection to maximize aspeed at which a buffer of the first peer is filled, and subsequently,preferentially downloading chunks of content from the one or more otherpeers connected to the first peer over a relatively high bandwidthconnection.
 10. The method of claim 4, further comprising using theheuristic engine for generating a download plan for accessing particularcontent from the one or more other peers using chunk information andnetwork status information obtained from the super-peer.
 11. The methodof claim 10, further comprising using the heuristic engine to determinechanges in the chunk information and in the network status informationand updating the download plan based on the changes, wherein theheuristic engine adapts the download plan to achieve at least one goalselected from a plurality of goals consisting of: starting apresentation of the content without delay; providing as high a qualitypresentation of the content as possible; keeping a buffer of the firstpeer substantially full with one or more chunks of content, even if theone or more chunks of content are of low quality; and finding highquality chunks of content that can be downloaded sufficiently fast tokeep the buffer of the first peer full.
 12. The method of claim 1,further comprising, prior to downloading the second chunk of contentfrom the third peer to the first peer: determining that the second chunkof content is not available at a requested bitrate; transcoding thesecond chunk of content into the requested bitrate; and storing thesecond chunk of content at the requested bitrate.
 13. The method ofclaim 12, wherein the heuristic engine operates in a plurality ofdifferent states, including: a fill state when a download of one or morechunks of content is initiated to fill a buffer, wherein chunks ofcontent are selected that will initially fill the buffer as quickly aspossible, and wherein priority is given to downloading chunks of contentthat are selected over relatively high bandwidth connections, ratherthan over relatively low bandwidth connections, and to downloadingchunks of content earlier in the presentation rather than later; amaintain state, after the buffer is full, wherein the heuristic enginetries to maximize a quality of the presentation that can be achieved,for current network conditions, by giving priority to higher qualitychunks of content that are encoded for transmission at a relativelyhigher bit rate over lower quality chunks of content that are encodedfor transmission at a relatively lower bit rate, so long as chunks ofcontent are available in the buffer in time to be accessed for thepresentation; and a recover state, if the buffer is emptying of chunksof content to a point where continuity of the presentation isthreatened, wherein the recover state is similar to the fill state, inthat downloading of lower quality chunks of content is given priorityover downloading of higher quality chunks of content, until the bufferis refilled at least a predetermined amount with chunks of content,thereby enabling the heuristic engine to return to operation in themaintain state.
 14. A system for enabling content to be transferredwithin a domain, comprising: one or more processors; memory storinginstructions that, when executed by the one or more processors, causethe system to perform operations, comprising: registering, based atleast in part upon a first peer connecting to the domain, the first peerwith a super-peer that stores information identifying other peers in thedomain; obtaining data that describes network conditions and identifiescontent available from the other peers, wherein the content is dividedinto chunks of content and wherein the chunks of content available fromthe other peers have been encoded for transmission at various bit rates;selecting a second peer from the other peers, and a first chunk ofcontent to download to the first peer from the second peer, wherein theselection of the first chunk of content is based, at least in part, upona bit rate for which the first chunk of content has been encoded fortransmission, an amount of bandwidth that is available for communicationbetween the first peer and the second peer, and a size of the firstchunk of content; downloading the first chunks of content from thesecond peer to the first peer; determining, based at least upon the datathat describes the network conditions, that the network conditions havechanged; selecting, based at least in part on determining that thenetwork conditions have changed, a third peer from the other peers, anda second chunk of content to download to the first peer from the thirdpeer, wherein the selection of the second chunk of content is based, atleast in part, upon a bit rate for which the second chunk of content hasbeen encoded for transmission, an amount of bandwidth that is availablefor communication between the first peer and the third peer, and a sizeof the second chunk of content; and downloading the second chunk ofcontent from the third peer to the first peer.
 15. The system of claim14, wherein a heuristic engine of the first peer selects the second peerfrom which to download the first chunk of content to maximize abandwidth for downloading the first chunk of content, and based on aquality of the first chunk of content.
 16. The system of claim 14,wherein a heuristic engine of the first peer selects a specific chunk ofcontent to be downloaded from another peer at a specified bit rate, orthe heuristic engine requests the specific chunk of content to bedownloaded and the super-peer determines an appropriate bit rate fordownloading the specific chunk of content from an appropriate otherpeer, or the super peer provides a web application to the first peerthat directs the first peer to another peer that will download thespecific chunk of content to the first peer.
 17. The system of claim 14,wherein a peer-to-peer stack manages communications over the networkbetween the other peers, and wherein a heuristic engine stores heuristicdata about the other peers.
 18. A system for enabling content to betransferred within a domain, comprising: a plurality of peers, includinga first peer that requests content to be downloaded from one or moreother peers, wherein the content is divided into chunks of contentstored by the one or more other peers, and wherein the chunks of contenthave been previously encoded for transmission at different bit rates;one or more super-peers with which the first peer is registered, the oneor more super-peers storing information identifying the other peers; anetwork connecting the plurality of peers and the one or moresuper-peers in data communication; wherein the first peer executes ahost application that starts a peer-to-peer stack that registers thefirst peer with a first super-peer of the one or more super-peers andreceives information identifying the one or more other peers from thefirst super-peer; the first peer selecting a first chunk of content tobe downloaded from a second peer of the other peers, the first chunk ofcontent being selected is based at least in part upon a bit rate forwhich the first chunk of content has been encoded for transmission, anamount of bandwidth available for a connection between the first peerand the second peer, and a size of the first chunk of content; and thefirst peer selecting a second chunk of content to be downloaded from athird peer of the other peers, the second chunk of content beingselected is based at least in part upon a bit rate for which the secondchunk of content has been encoded for transmission, an amount ofbandwidth available for a connection between the first peer and thethird peer, and a size of the second chunk of content.
 19. The system ofclaim 18, further comprising a heuristic engine associated with thefirst peer and wherein the heuristic engine selects the second peer fromwhich to download the second chunk of content to maximize a bandwidthfor downloading the first chunk of content, and based on a quality ofthe first chunk of content.
 20. The system of claim 19, furthercomprising heuristic data stored by the heuristic engine, and whereinthe heuristic data includes one or more of: an identity of the otherpeers on the domain; a location of the other peers on the domain; anetwork latency; an available transmission bandwidth between points inthe domain; an identification of chunks of content available at theother peers on the domain; a location of one or more super-peers on thedomain; and an identity of the one or more super-peers on the domain.